The present invention relates to a capacitor arrangement and a method for operating a capacitor arrangement.
Power electronic systems are increasingly being used in stationary applications, such as, for example, in wind turbines, as well as in mobile applications, such as, for example, in electric and hybrid vehicles. These power electronic systems, for example, enable a connected electrical machine to be operated at a variable rotational speed or to generate an output voltage which deviates from an input voltage. As a rule, said power electronic systems are supplied with a DC voltage which is supplied via a pulse width modulated inverter, also referred to as inverter. A so-called DC link, via which the power electronic system is connected to the DC voltage source, is characteristic for such systems. In order for the DC link to also be able to dynamically provide the currently required power, the DC link is buffered with a DC link capacitor. Said DC link of the power electronic system is furthermore electrically connected to power semiconductors, for example IGBTs or MOSFETs. The connection should preferably be implemented in a low-resistance and low-inductive manner and as short as possible, so that an overvoltage resulting at the power semiconductors during a switching operation remains small.
The German patent application DE 10 2012 218 579 A1 discloses, for example, a low-inductivity capacitor module and a power system comprising such a low-inductivity capacitor module. In this case, a multiplicity of capacitors is disposed on a metalized substrate. A set of capacitors from this multiplicity of capacitors is each connected in parallel.
When operating such a power electronic system, a power loss occurs particularly in the power semiconductors. As a result, the power electronic system warms up. Not all of the components, however, warm up to the same extent. In addition, the different materials used expand to a varying degree. It is thus possible for mechanical stresses to result in the power electronic system, in particular between the power modules and the DC link.
There is therefore the need for a capacitor arrangement which allows for a connection between DC link capacitor and switching modules which has inductance values that are as low as possible. There is further the need for a capacitor arrangement which enables mechanical stresses between the DC link and switching modules to be prevented or at least minimized.